In order to meet the increasing demand for wireless communication services, efforts have been made to develop improved or pre-5G or 5G communication system.
In a foreseeable future 5G wireless communication network, better services could be provided by deploying a large number of small cells below the existing macro cell to improve cellular network capacity. Further, carrier aggregation (CA) could also be an effective way to increase the data rates. When carrier aggregation is utilized by a wireless communication system, each component carrier could be considered to serve an individual cell. Each cell may have a different coverage range or may overlap with another cell partially or completely. When carriers are aggregated, each carrier is referred to as a component carrier. For general macro-assisted architecture, the primary component carrier (PCC) would serve the primary serving cell Pcell (i.e., macro cell) and could provide most or all of the signalling transmissions for both uplinks and downlinks. While the secondary component carrier (SCC) would serve a secondary serving cell Scell (i.e., small cell) for downlinks and possibly uplinks and would mostly be used carry user data.
On the other hand, the Millimeter Wave (mmWave) communication is an emerging technology endowed with large spectrum resources as the technology operates on one or more frequency bands between 30 GHz and 300 GHz. Because of the high path loss associated with the mmWave communication, usually highly directional antenna having a large aperture. However, wireless communications using directional antennas would require transmissions in appropriate directions. In such scenario, the direction or position in the angular domain of each of the UEs relative to the base station would need to be known in order to allocate resources for the UEs. To obtain the direction of UEs and conditions of channels, a base station conventionally rely upon transmitting reference signals in exchange for channel condition information received from UEs.
When combining mmWave communication with carrier aggregation architecture, beam configuration should be appropriately configured for a dual-connecting UE in order to provide control signaling and data transmission for directional mmWave communications. However, since reference signals are generally periodic transmitted, how to effectively transmit control signaling and then data transmission in a beam direction in a non-periodic way has been an important goal to be achieved by the persons skilled in the field.